I tried doing that, but it was a pain. In addition 2 lights, more weight on the helmet, 2 sets of batteries to charge and recharge. The biggest problem was just that when I tried to look behind me (often at a stoplight) I'd flash anyone in a next next to me right in the face. I stopped both because it was rude, and choosing between either not being able to look behind me or really pissing off the driver of a 2 ton vehicle right before we were both on the road seemed like a bad idea.